Cannas can be grown the year round in Florida and southern California (zone 9) or wherever average annual winter temperatures dip no lower than 20F. Elsewhere, they must be grown as summer bedding plants, since the roots cannot withstand frost.
Locating And Planting Canna
Cannas normally arrive from the nursery as dormant tubers or rhizomes, which are their rootstock. Each tuber will have 2 to 5 "eyes", or buds, on it. For earliest bloom, start these roots indoors 4 weeks before the last spring frost, and plant them in a sunny location outdoors only after the last frost. For details see Starting Summer Bulbs Early. Or, plant tubers directly in the ground well after danger of frost is past and when the soil temperature is at least 65°F. This will be about the same time for planting corn and tomatoes. Cannas do best in moist, rich, well-drained soil that is acidic (pH 6.0 to 6.5).
Depth - Plant the tubers 3-4 inches deep and 1 1/2 to 2 feet apart.
Prevent Animal Damage - If in the past you have had problems with critters digging up and eating your newly planted bulbs, you may want to consider soaking the bulbs in a repellent of some kind before they are planted. See the file on Selecting a Repellent for Bulbs.
Keep the bed free of weeds.
Tall types will need need staking.